<p>Just when I thought I had perfected the math section..</p>
<p>Here's the question:
If 0<x<8 ahd -1<y<3, which of the following gives the set of all possible values of xy. </p>
<p>I just multiplied the two sets and got 0<xy<24, but apparently the real answer was -8<xy<24. Anyone care to elaborate on how such an unfortunate turn of mathematical events occurred?</p>
<p>You have to think about the combination that can yield the lowest value and then the combination that can yield the highest value. You get the lowest value with negative 1 as y and a big positive x value, so (-1, 8), which is -8. You get the highest value with two big positives, so (8, 3), which is 24.</p>
<p>Edit: looks like silverturtle beat me to it. :(</p>
<p>Set A:
0<x<8</p>
<p>Set B:
-1<y<3</p>
<p>Multiply the biggest number in Set A by the biggest number in Set B.
3 x 8 = 24 = maximum value</p>
<p>If all the numbers were positive then it would make sense to multiply the smallest number in Set A by the smallest number in Set B. Since there is a negative you need to realize the smallest negative x the greatest positive will yield the smallest number.</p>
<p>-1 x 8 = -8 = minimum value</p>
<p>-8<xy<24</p>